1. Field of the Invention
This invention relates to a continuous screw driving tool, and more particularly to a screw feeding device in a continuous screw driving tool.
2. Description of the Related Art
Referring to FIGS. 1, 2, and 3, a screw feeding device in a continuous screw driving tool disclosed in U.S. Pat. No. 5,988,025 includes a casing 1 mounted on a tool body of the continuous screw driving tool. A feeder box 2 is movable reciprocally within the casing 1, so that a screw carrying belt (not shown) is fed by a distance corresponding to one pitch of screws (not shown) carried thereon as the feeder box 2 is moved reciprocally by one stroke. A stopper base 3 is mounted on the feeder box 2, and a mounting mechanism is provided for mounting the stopper base 3 on the feeder box 2, so that the stopper base 3 can be changed in its position relative to the feeder box 2. The mounting mechanism includes a plurality of lock holes 302 and a lock member 4. The lock holes 302 are formed in the stopper base 3. Any adjacent two lock holes 302 are spaced apart from each other by a predetermined distance in a screw driving direction (X). The lock member 4 is movable within a vertical slide slot 202 in the feeder box 2 in a vertical direction (Z), and has a lock protrusion 403 engageable with a selected one of the lock holes 302 and held in position in the screw driving direction (X) relative to the feeder box 2.
The screw feeding device suffers from the following disadvantages:    (1) The stopper base 3 is formed with a plurality of sliding members 301 engaging respectively and movably a plurality of open-ended horizontal slide slots 201 in the feeder box 2. As such, when the lock member 4 is pressed in the vertical direction (Z) to remove the lock protrusion 403 from the selected lock hole 302, unintentional removal of the stopper base 3 from the feeder box 2 may occur. Furthermore, if the unintentional removal of the stopper base 3 occurs, two compression springs 5 will jump and drop from the feeder box 2, thereby resulting in inconvenience during use.    (2) Since any adjacent two lock holes 302 are spaced apart from each other by the predetermined distance, as described above, the number of the lock holes 302 is limited. As a result, the applicable range of the continuous screw driving tool is also limited.    (3) Visual inspection of the screws is not permissible during the screw driving operation due to the fact that screw-discharging hole 203 and lateral side surfaces of the feeder box 2 are shielded by the stopper base 3. To facilitate alignment of the screws, a central slot unit 304 is provided at the stopper base 3, and is in spatial communication with a screw feeding hole 303 in the stopper base 3, thereby further resulting in inconvenience during use and reducing the alignment precision.